This invention relates to a process for producing carbonated coffee drink, in which the bubbling from such coffee drink is suppressed, while maintaining body, taste, and flavor which are essentially that of freshly brewed coffee.
The carbonated coffee drink is generally produced by mixing coffee extract with carbonated water, or by impregnating the coffee extract with carbon dioxide to carbonate the same. The thus produced carbonated coffee drink is generally charged into various types of container for transportation and sale.
As has already been acknowledged by all connoisseurs, the quality of coffee is determined by the body, taste, and flavor which it has. All of these qualities are so important in the brewed coffee that they are deservedly called "the soul of coffee." The body, taste, and flavor are created by various constituents in the coffee. Of these constituents, colloidal material is one of the most important constituents in the coffee. That is, this colloidal material constituents an important element for imparting the body, taste, flavor to the coffee, from which the smoothness of coffee is also derived. At the same time, however, this substance accelerates bubbling of the coffee, although its absence deprives the coffee drink of its body, taste, and smoothness.
It will be appreciated that the aforementioned coffee extract contains a large amount of the colloidal material, and hence the aforedescribed carbonated coffee drink produced by using such coffee extract naturally contains a large amount of such colloidal material. On account of this, the coffee drink bubbles intensely at the time that it is charged into a container, or upon opening of cans or pulling of caps off bottle containers, or upon pouring the drink from the container into receptacles therefore, thus causing a large quantity overflow of the drink from such container or receptacle. As the result of this, it becomes necessary to suppress the bubbling from this carbonated coffee drink to the greatest possible extent. With a view to suppressing such undesirable bubbling, various processes have heretofore been practiced, wherein an attempt has been made as to removed or degrade the colloidal material which is the principal cause for such bubbling.
The following processes, for example, are well known: (1) a process, in which the colloidal material is physically removed from the coffee extract by filtration or separation using, for example, asbestos, diatomaceous earth, or microfilters; and (2) a process, in which the colloidal material is enzymatically degraded by admixing various kinds of enzymes such as protease, tannase, amylase, etc., into the coffee extract.
However, according to these known processes, the body, taste, and flavor inherent in the freshly brewed coffee are seriously impaired in such processed coffee drink, although the suppression of undesirable bubbling has been accomplished, since each of these known processes comprises removing or degrading the colloidal material. Accordingly, the thus obtained coffee drink tastes bland.
It has been said that retention of flavor of the extracted coffee extract (or liquid coffee) at a normal temperature is one of the most difficult problems in the production of coffee drinks, and has even been considered impossible.
Generally speaking, change in the flavor of liquid coffee is mostly ascribable to oxidation due to oxygen in the air. In order to prevent or decrease such undesirable oxidation, there have been practiced various expedients, among which are: (1) vacuum packing of the coffee extract; (2) deaeration of the liquid coffee to remove oxygen dissolved in the liquid; (3) substitution of an inert gas; for oxygen and so forth.
Of the abovementioned representative methods, when the third method is employed to carbonate the extracted coffee with carbon dioxide gas as the inert gas, it is recognized that, with increase in the volume of carbon dioxide gas, the change in the coffee flavor becomes reduced, and its preservation is heightened. At the same time, this increase in the gas volume is also recognized as contributing to sterilization of the coffee extract. In view of the fact that coffee extract has a high pH value, an additional sterilization process is particularly required to preserve it in a liquid form. For this purpose, there has been adopted the ordinary high temperature sterilization process, although it is not desirable from the standpoint of the flavor retention.
Especially, according to the latter process, the obtained coffee drink is liable to give out an unpleasant odor attributable to the odor of enzymes or produced by the enzymatic degradation. Hence, it cannot be said that the enzymatic process is preferable. Furthermore, each of the processes comprises complicated process steps, and necessitates complicated installations.